[infinispan-dev] IRC meeting

[Dan Berindei]

Hi Pedro

We've talked about sending PREPARE_VIEW commands through SEQUENCER as
well, but it would only work if we could make it really synchronous
(i.e. we can get the response from all the targets). The state
transfer fails automatically when we notice another node leaving - so
having the state transfer succeed on the originator does not guarantee
success on the other nodes as well.

It would also be more inconvenient to use different protocols for each
cache, since the component that sends PREPARE_VIEW commands is global,
but that wouldn't be a show-stopper.

A representative failing test is
TotalOrderStateTransfer1PcTest.testSTWithWritingNonTxTest (it's
actually using implicit transactions, but it doesn't matter). There
are two ways I've seen it fail:
1. It appears that SEQUENCER doesn't start delivering TO messages
right away after a node joins. It's not very clear to me why this
happens, but I see in the logs (http://pastie.org/3843863) that both
nodes receive the prepare message, yet only the SEQUENCER on the
originator logs that it delivered the message.
2. We're releasing the state transfer lock while waiting for the total
order thread to execute the prepare. This means there is a window
between the ST lock release in the user thread and the ST lock acquire
in the total order thread, where a node could join and start receiving
state - but not this prepare command. I suspect this could be fixed by
sending PREPARE_VIEW through SEQUENCER, but it is rather hard to
reproduce, I only saw it when I added lots of logging (above the
regular TRACE logging) to debug the first issue.

Cheers
Dan


On Mon, Apr 30, 2012 at 8:41 PM, Pedro Ruivo <pruivo at gsd.inesc-id.pt> wrote:
> Hi all,
>
> I've looked at the IRC meeting and I've noticed that the State Transfer
> is not working in the Total Order based protocol. I am wondering, if it
> is not enough to send the prepare view command in total order. In this
> way, all the nodes will deliver the command in the same order, and then,
> all the nodes are in the same state when the command is delivered.
>
> What do you think?
>
> If you have questions, I'm available to help.
>
> Cheers,
> Pedro Ruivo
>
> On 4/30/12 3:48 PM, Galder Zamarreño wrote:
>> Minutes of our last IRC meeting can be found here:
>> http://transcripts.jboss.org/meeting/irc.freenode.org/infinispan/2012/infinispan.2012-04-30-14.20.html
>>
>> Cheers,
>> --
>> Galder Zamarreño
>> Sr. Software Engineer
>> Infinispan, JBoss Cache
>>
>>
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